CD8A and idiopathic pulmonary fibrosis: Previous studies of immunohistochemical analysis including the TLs subpopulations of lung tissue in IPF [5,8,28,29] and other interstitial pneumonias [30] have shown that the inflammatory process is mainly mononuclear, and that both CD4+ and CD8+ TLs were well represented and diffusely distributed in the interstitium, with an additional component of the CD4+ TLs observed inside lymphoid follicles.